The invention relates to a power conversion system, and, more particularly, to a photovoltaic power converter system with a controller configured to actively compensate harmonics that may be drawn by a load coupled to the photovoltaic system.
Environmental concerns and the search for alternative sources to generate electrical energy suitable for supplying households or small commercial sites have driven the need for power converter systems, such as photovoltaic array converters that can process sunlight into a standard and usable electrical form, e.g., supplying energy to the mains grid during daylight hours.
It is known that many of these photovoltaic array converters simply inject a unity power factor sinusoidal current onto the mains grid supply thereby reducing the total energy drawn by the local load from the mains grid supply. Loads on the local grid can draw currents, which may contain harmonics. These harmonic currents can potentially disturb the mains grid supply and other loads on the system. For example, these harmonic currents may lead to poor utilization of the grid supply and can cause voltage distortions and, in severe cases, cause other loads on the same supply to malfunction.
Some power electronic systems may be designed not to draw harmonic currents and are referred to as low Total Harmonic Distortion (THD) unity power factor converters. However, not all loads draw unity power factor with a low THD and it is for these loads that compensation is needed. The number of the loads that can generate harmonic currents may further aggravate the problem. Large active power compensators installed by power utilities are sometimes used on the mains grid supply to reduce the harmonic currents that are present on the system and various main nodes. These large and bulky systems unfortunately are limited in the number of the harmonics that can be compensated for, are expensive and generally do not reduce the harmonic currents at all points on the mains grid.